Generally, the potential for biosolids (digested or composted) to contribut
e heavy metals to the soil-plant system has been compared with commercial f
ertilizers and other organic wastes but not with biosolids-ash. An column s
tudy was conducted in a greenhouse to determine the availability, extractab
ility and leachability of metals in a degraded, non-calcareous soil amended
with different biosolids (200 Mg ha(-1)). The biosolids investigated were
dewatered, anaerobically digested biosolids, composted biosolids and biosol
ids-ash. The columns (26 cm) were planted with wheat (Triticum aestivum L.
cv Mexa). The addition of digested biosolids decreased the dry matter yield
of wheat. Treatments including organic biosolids increased Cu and Zn conce
ntrations in wheat roots, straw and grain, whereas the addition of biosolid
s-ash did not affect the concentrations of these metals in wheat. Concentra
tions of Ni, Co, Pb, Cr and Cd in wheat were below reliable detection limit
s (0.06, 0.05, 0.1, 0.06 and 0.02 mg kg(-1), respectively). After harvestin
g, total and AB-DTPA extractable Cu, Zn and Pb increased in the upper layer
of the soil amended with the different biosolids studied, whereas levels o
f AB-DTPA extractable Ni and Co were affected only when the soil was amende
d with digested or composted biosolids. Total chromium increased only in tr
eatments including organic biosolids. The AB-DTPA extractable Cu, Zn and Pb
in the lower layer of the soil in treatments including biosolids evidenced
downward movement of these metals. However, absence of these metals in col
umn leachates indicates that this movement was gradual.